Control system using multiple winding saturable reactors



Dec. 14, v 1954 w. J. BROWN 2,697,197

CONTROL SYSTEM usmc MULTIPLE WINDING SATURABLE REACTORS Filed Aug. 17, 1949 e Sheets-Sheet 1 POWER CONVERTER SOURCE I INVENTOR. WALTER J. BROWN w. J. BROWN 2,697,197

WINDING SATURABLE REACTORS Dec. 14, 1954 CONTROL SYSTEM USING MULTIPLE 6 Sheets-Sheet 2 Filed Aug. 17, 1949 INVENTOR.

BROWN WALTER W. J. BROWN Dec, 14, 1954 CONTROL SYSTEM USING MULTIPLE WINDING SATURABLE REACTORS 6 Sheets-Sheet 5 Filed Aug. 1'7, 1949 INVENTOR.

BROWN WALTER .1 BY

W. J. BROWN Dec. 14, 1954 6 Sheets-Sheet 6 Filed Aug.

v R 0 I'll T twm m 6N w mm 3 3% 5 \Fmimmw W 7 1 5 A 3N n A M 7 m3 8N ww w WALTER J. BROWN BY United States Patent CONTROL SYSTEM USING MULTIPLE WINDING SATURABLE REACTORS Walter J. Brown, Cleveland Heights, Ohio Application August 17, 1949, Serial No. 110,813 21 Claims. (Cl. 321-49) a phase shifting network having a saturable reactor as and Saturable Reactors Using network connected to the load.

In this specification, the term passive network is one which contains no amplifier, and may include one or more circuit elements. A passive connection likewise means a connection containing no amplifier and may include a direct connection Without any circuit elements whatever.

Another object of the invention is to provide in the control system mentioned above a and wherein another of the windings is effectively connected in series with at least part Anotherobject of the invention is to include in con- JUIlClIlOIl w th the control system recited above a source bined result of the two w1ndings is to provide a comto the load.

tions of a C011 or coils, extending of terminals or tappings.

A further obiect system. a rectifier concurrently herewith, entitled Saturable Reany of the kinds above mentioned, in which the load comprises the armature or field of a generator or motor, in conjunction with a tachometer, if desired.

et another object of the invention is to inhibit the reversal or effect of reversal of asymmetric flux in the to provide a control system of the kind described, for the purposes of conconverter comprising a motor-generator or other power-driven generator, controlled by a spacedischarge device.

. 770,968, filed August 28, 1947, now Patent No. 2,524,761; Phase Shift Network, Serial No. 770,966, filed August 28, 1947, now Patent No. 2,524,759; Phase Shift Bridge, 770,967, filed August 28, 1947, now Patent No. 2,524,760; and Phase Shift Circuit, Serial No 779,909, filed October 15, 1947, now Patent 2 Other objects and a fuller understanding of the invention may be had by referring to the following description and claims, taken in conjunction with the accompanying drawings, in which:

Figure 1 is a schematic block diagram of a load supplied trolling asymmetric magnetizing energgy;

is a vector diagram of the voltage vectors obtalnable from the phase shift circuit included in Figure 2;

Figure 4 is a modification which may be substituted for part of Figure 2;

Figure 5 is a pictorial view of a saturable reactor having a rotatable cylindrical permanent magnet as a source of controlling asymmetric magnetizing energy;

Figure 6 is a schematic wiring diagram for the windings of the saturable reactor shown in Figure 5;

Figure 7 is a further modification of my control circuit wherein the controlling source of asymmetric magnetizing energy is a source of asymmetric electromotive force and the rectifier in series with the of the saturable reactor is accordingly reversed;

Figure 9 is a still further modification for the circuit arrangement of Figure 7 showing a motor field control arrangement having a rectifier in parallel rather than in series with the direct current winding of the saturable reactor;

Figure 10 is a further modification of my control circuit wherein enerator field control is used, and one direct current winding on the saturabe reactor is used for the resultant of the controlled and the controlling asymmetric electromotive forces and also has a rectifier paralleled thereacross, and further the saturable reactor has an anti hunt winding;

Figure 11 is a still further development of the invention wherein the saturable reactor controls a mercury arc rectifier supplying power to a motor armature and wherein the controlling source of asymmetric magnetizing energy is an additional winding connected to a source of asymmetric electromotive force, and wherein the satalso has an antihunt winding, a current limit winding, and a compounding winding; and

Figure 12 is a further development of my invention wherein the saturable reactor has a permanent magnet as the source of controlling asymmetric magnetizing energy and wherein a polarized armature is shown to inhibit reversal of the asymmetric magnetomotive force in the saturable reactor, and including a plurality of direct current windings.

Figure 1 shows a block diagram of a power converter 15 deriving power from a power source 16 and supplying power to a load 17. The power converter 15 is controlled by a passive network 18 which includes generally a passive circuit 19 and the alternating current winding or windings 22 and 23 of a saturable reactor 20. An electrical source 21 supplies power to the passive network 18 for use in control purposes. The saturable reactor includes an alternating current winding comprising coils 22 and 23 and a direct current winding 24. A second passive network 25 includes as part thereof the direct current winding 24 and a passive connection 26, which may be a direct pair of connections, or which may include other passive circuit elements. The passive connection 26 is illustrative of a passive circuit or of a direct connection. The passive network 25 is adapted to develop in direct current winding 24 a controlled asymmetric voltage or current derived from the load 17 through leads 27 and passive connection 26, which controlled voltage or current is in accordance with some characteristic of the load, such as a terminal characteristic of an electrical load. This results in the flow of an asymetric current in the direct current winding 24 which establishes an asymmetric magnetomotive force in the core of the reactor, thus constitut'ng means for establishing a controlled source of asymmetric magnetizing energy passively derived from the load. Additionally, a controlling source of asymmetric magnetizing energy is also provided, and is shown schematically as an arrow 28. Said controlling source of asymmetric magnetizing energy may take the form of a permanent magnet adjacent to or forming part of the core, or a source of asymmetric electromotive force connected to an additional winding on the core, or it may take the form of a controlling asymmetric electromotive force which is applied to the passive network 25 so as to control the asymmetric current in the direct current winding 24.

The Figure 2 shows a specific and simple circuit arrangement of the invention wherein a power converter 31 for the purpose of illustration has been shown as a full wave gaseous or vapor rectifier system employing space discharge tubes such as gaseous or vapor tubes 32 deriving alternating current power from a transformer 33 which is adapted to be connected at the terminals 34 to an alternating current source, not shown. The power converter 31 is adapted to supply rectified alternating current power to a load 35 shown specifically as the resistance 36.

The converter 31 is adapted to be controlled in this particular embodiment to apply a constant current to the load resistance 36. To this end a control resistance 37 is connected efiectively in series with the load resistance 36 and forms part of a passive network 33. The passive network 38 also includes a direct current winding 39 of a saturable reactor 4% wherein the saturable reactor also has an alternating current winding 29 comprising coils 41 and 42, forming part of a second passive network 43. The passive networks 38 and 43 and the saturable reactor comprise generally the control system 44. The passive network 43 is shown as a variable impedance network and in this particular embodiment is shown as a phase shifting network.

The passive network 43 is shown as including a phase shifter 45 which has resistances 46 and 47, preferably of equal resistance values, energized from a winding 48 on the transformer 33. A resistance 49 and a condenser 50 are connected across the serially connected resistances 46 and 47. Serially connected across the resistance 49 is a condenser 51 and the alternating current winding 29 of the saturable reactor 40. The output voltage of the phase shifter 45 which is shaftable in phase relative to the input voltage across t. e resistances 46 and 47 is obtained between the terminal 52, which is the junction of the resistances 46 and 47, and the terminal 53 which is the junction of the condenser 51 and the alternating current winding 29. Across these two terminals 52 and 53 is placed an impedance network having an effective center tap, such as a center tapped grid transformer. In this specific embodiment resistors 54 and 55 have been with a center tap 56. Condensers 57 and 58 are shunted across the resistors 54 and 55, respectively. The phase shiftable output voltage of the phase shifter 45 is thus obtained across the resistors 54 and 55 and is applied to the space discharge tubes 32 to control the firing angle thereof.

The saturable reactor 40 is shown as including a cylindrical permanent magnet 59 in the middle leg 66 of the core of this reactor 40. This permanent magnet 59 is magnetized across a diametral plane and is adapted to be rotated about its axis through degrees, thus keeping the air gap between the permanent magnet and the middle leg 60 substantially constant but which upon rotation varies the asymmetric magnetizing energy applied to the saturable reactor 40. A filter circuit 61 is shown as a T-type filter and preferably is resonant at the main ripple frequency of the converter which for a 60 cycle alternating current input would be a cycle ripple for the full wave rectifier system shown.

The Figure 3 shows a vector diagram of the voltages obtainable across the phase shifter 45 with the vectors E45 and E47 being in series as the alternating current input voltage. The voltages E50 and E49 designate the voltages across the condenser Sit and resistance 49 which are serially connected across the alternating current input terminals. The condenser 51 and alternating current winding 29 have vectors E51 and E29 shown on the vector diagram as spanning the vector E49. By variation of the impedance in the alternating current winding 29 the po tential at the terminal 53 which is shown on the vector diagram as 53 may be varied relative to the voltage across the alternating current input vectors E46 and E41. The output voltage Emil, is shown as being between the points 52 and 53 with the point 52' near the center of a closed path 62 upon which lies the locus of the point 53. This particular phase shifter is a specific embodiment of the various forms of phase shifting networks shown in my copending applications mentioned above. With the voltage vectors as shown in the Figure 3 it will be seen that the output voltage vector Eoul; from the point 53 to the point 52 would lag the alternating current input voltage substantially 90 degrees and hence the tubes 32 would be delivering about half maximum output.

If the reactance of the alternating current winding 29 is increased beyond the value shown in Figure 3, the point 53' will be moved clockwise along the locus 62, and the output voltage vector Ecut will lag the alternating current input voltage vector Edit-E47 by more than 90 degrees; by making the reactance of the winding 29 sumciently high in relation to the reactance of condenser 51, the output voltage vector Eoui', may be made to lag the alternating current input voltage vector Ere-E47 by nearly degrees so that the tubes 32 would be delivering sub stantially zero output. The initial phase angle between the output and input voltages, when no direct current magnetizing energy is applied to the saturable reactor, may accordingly be predetermined by designing the alternating current winding 29 to have the appropriate reactance values. Now, when direct current or asymmetric magnetizing energy is established in the core of the saturable reactor, the reactance of alternating current winding 29 will be diminished, point 53 will be moved anticlockwise along the locus 62, the lag of the output voltage Emir with reference to the input voltage E4sE41 will be decreased, and the output of tubes 32 will be increased.

The control system shown in Figure 2 is designed to supply substantially constant current to the load resistance 36. As some condition in the system would change, such as a lowering of the impedance of the load resistance 36, more current would tend to flow to this load resistance, and hence a greater voltage drop would occur across the control resistance 37. This greater voltage drop across the resistance 37 would supply a greater voltage to the direct current winding 39. The increased voltage on the direct current winding 39 increases the asymmetric magnetromotive force supplied by such winding. The asymmetric magnetomotive force supplied by the permanent magnet 59 is preferably in opposition to the magnetornotive force supplied by the direct current winding 39 and overbalances such latter magnetomotive force so that the resultant asymmetric magnetomotive force applied to the core of the saturable reactor 4% is the difference between the two. Now when the voltage to the direct current winding 39 is increased this causes a decrease in the net resultant asymmetrlc ma netomotive shown 35 force applied to the saturable reactor 44 which thus increases the impedance of the alternating current winding is a diode blocking rectifier to allow current to continue 29. hlS shifts the p01n t 53 on the vector diagram of to flow in the inductive field winding during the reverse current winding 39 decreases, the resultant asymmetric network 43A. The reactance of magnetomot ve force on the saturable reactor 40 inwinding 29 is preferably made very high in relation to creases, the impedance of the alternating current Winding the reactance of condenser 51 so that the load resistance 36.

e Figure 4 is a porated into the circuit of Figure 2 wherein the load bl ea tor 93 includes the a resistance 36 is supplied with a substantially constant 2 voltage. The circuit of Figure 4 shows the load 35A and d an antihu t winding 94. The antih a passive network 38A which may be substituted for the di t u ent windings 94 and 95 form load 3 and passive network 38 in the circuit of Figure t k 96 The passive network 96' includes a potentiom- 2 The dlrect current winding 39 for the saturable react 97 whi h is adapted to be energized from an tor 40 15 8 Own as before but 18 shown as being C011" asymmetric voltage source shown as the direct current nected across a resistance 63 which is serially connected battery 98 A ontrol resistance 99 is c w1th another resistance 64 which series combination is l i Series with the motor armature 88 and is shown as paralleledacross T116310ad rfiisfane Thlls, Thfi direct part of the passive network 96 since a voltage is developed current winding 39 is supplied with a voltage dependent thereacross hi h upon the voltage applied to the load resistance 36 and 1s ili d i h control ystem 83 so onnected effectiveance 36. A passive connection may be used rather than one d th f o e t d to the contr he tachometer 89 has positive and negative terminals urable reactor 65, such as has been diagrammatically 103 and 104, respectively. A speed control tap 105 is depicts?! In the clfcult 0f Pjlgllre The satul'flblfi r636 provided on the potentiometer 97 and is connected to the 65 Includes a Core, haYlng generally first: Second a negative terminal 104. The positive terminal 103 of the thlfd legs 5 67 and 63 With first and Second altfimfltmg tachometer 89 is connected through a flux reversal pre- Current C0115 69 and 70 Wound about first and thlrd vention rectifier 106 and an optional resistor 107 to the legs 66 and 68, respectively and serially connected to main form an alternatmg current winding. The middle leg 40 first and second pole pieces 73 and 74. Direct current 1 coils 79 and are disposed about the first and second plied to h portions 71 and 72, respectively, of the second leg 67, and ence between these two voltages are serially connected to form a direct current winding. 45 The antihunt Winding 94 is connected by an antihunt Permanent magnet 75 Shown as b81113 cyhndncal condenser 108 to the negative lead 109 of the armature circuit of the motor armature 88. The other end of the a t'hunt w'ndin 94 s connected b a lead 110 to the cylindrical shape to conform to the cylindrical shape of l g l y the permanent magnet 75 and thus reduce the air ga therebetween. The permanent magnet is adapted to be 0 and a rotated through degrees about the axis 76 to thus th shift the position of the poles of the magnet 75 relative tween the lead 110 an to the pole pieces 73 and 74. By such a rotational shifting the asymmetric magnetizing energy supplied to the saturable reactor 65 may be varied at will. u

e main direct current winding is the ditfer- 60 motive force. This resultant asymmetric electromotive force is applied to the main direct current winding 95. referably the voltage obtained from the potentiometer 97 exceeds that voltage obtained from the tachometer 89 such across the term1nals 81 and S2. The terminals 77 and 78 that the right qn'd of the Winding g5, as Shown in Figure r 7, is more positive than the left end thereof. This pro- Current Wmdmg of the samrable reactor 40 to the Phase 0 duces a resultant asynn'netric magnetomotive force in the core of the saturable reactor 93. The voltage between the terminal 101 and the variable tap may be considnetwork 38 as shown in the Figure 2 ered as a reference or controlling voltage for establishing The Figure 7 shows a more comprehensive control system 83 used to control the output of a power converter 4.11, t 1e .e t

84 comprising a controllable rectifier wh1ch supplies rectlfi i fg gg ggfii g sg ig a cggtiiii i $1 122 o f zs i ri ffied alternating current power to a generator field 85 of a mptric magnetizing energy geperator The armatufe of the generator. may be i en the contfolling voltage is zero and the load t l iown iri ilig tifiaaigg iil g f g g g 33:51: a voltage is zero, no current will flow through the winding ered as part of the converter 84 an d supplies enersy to a and accordingly h reactor Its maxlrmim Yoad 87 which is shown as including a motor armature 88 reacifmce zindifccordmg the vector diagrams .3 and a tachometer 89. and which may include a mechanical gnmon anglfi W111 be retarded lam/"119g Dad not shown The motor armature 88 has a field 30 the circuits are correctly phased, the power converter will upp h'ed from a separate ource not shov n The condevelop ZCI'O output, and a stable but inoperative condition 'erter 841s shown as including a controllable rectifier tube will eXlSt- If the Controllln" Voltage 15 HOW Increased; a 0 be ng suppl ed w th alternatmg current power through current Wlll flow through the Wlndln 95 thus CdllCl'lg transformer 91 from an alternating current source not the reactance of the alternating current winding 29 of the hown. A second rectifier tube 92 is not controlled but 35 reactor andcaus n the g i ion angle to advance. an um converter 84 to develop an output voltage which will increase as the controlling voltage is increased. The direct current voltage applied to the winding 95 from the load, or in other words the controlled asymmetric voltage, will, under these conditions, always remain somewhat below the controlling voltage and the difference therebetween will develop a current and therefore a rn'a'gnetomotive force in the winding 95 sufiicient to advance the ignition angle to the required degree. Owing to the high sensitivity of the phase shifting arrangement, a very smal change in current in the winding 95 will produce a large change in the ignition angle, and consequently the direct current output voltage of the converter 84 will closely follow, or will be closely proportioned to, the controlling voltage, and furthermore the operation can be made to occur in a stable manner, any rise in controlling voltage being followed by a rise in direct current load voltage; any slow fall in controlling voltage will be followed by a fall in direct current load voltage. However, a sudden fall in controlling voltage may produce an unstable condition, especially if the direct current load is of a type involving electrical or mechanical inertia, for instance, if it is highly inductive, or if it comprises a rotating machine having mechanical inertia and developing a counterelectromotive force. In such instances, if the controlling voltage is decreased too suddenly, the direct current load voltage may be temporarily maintained for sufficient time for the controlling voltage to drop below the voltage derived from the load, hus reversing the current in the saturating winding and thereafter causing the saturating current to increase, thus decreasing the reactance, advancing the ignition angle, increasing the direct current converter output and causing instability and possible disaster.

According to a further feature of this invention, I prevent the accidental reversal of the saturating flux in the reactor by including a small rectifier, preferably a dryplate rectifier 106, in series with the saturating winding.

The rectifier 106 is so polarized that the current flows from left to right as shown in Figure 7, which means that electron current flows in the opposite direction. Thus as long as the right end of the rectifier 106 is negative relative to the left end current will flow in this loop which includes the tachometer 89, the potentiometer 97 and the direct current winding 95. However, should the voltage obtained from the tachometer 89 ever exceed the voltage from that portion of the potentiometer 97 which lies between the terminal 101 and the variable tap 105 this flux reversal prevention rectifier 106 will prevent current from flowing in this loop circuit and will accordingly prevent or inhibit reversal of the resultant asymmetric magnetomotive force in the saturable reactor 93; under these conditions, the resultant asymmetric magnetomotive force will fall substantially to zero instead of reversing, and the reactance of the alternating current winding 29 will increase to its maximum, thus retarding the ignition angle of the tube 90 and reducing the output of the converter 84 substantially to zero, whereupon the motor 88 will slow down until the output of tachometer 89 has fallen to a value less than that of the controlling voltage.

The antihunt winding 94 is provided to limit the hunting in speed of the motor armature 88. The antihunt condenser 103 will pass current only during changes of voltage, and hence the antihunt winding 94 will be asymmetrically energized only during speed or load changes, and such energization is so polarized to stabilize the changes of speed of the motor armature 88.

The current limit rectifiers 111 and 113 are provided to limit the current supplied by the converter 84 during forward and reverse current directions, respectively, in the motor armature 88. The forward current limit rectifier 111 obtains through the variable tap 112 an adjustable voltage which is negative relative to the potential at the terminal 101. A current limit controlled voltage is obtained from the control resistance 99 which will be positive at the left end thereof when the generator 86 is supplying current to the motor armature 88. Should the forward armature current increase until the sum of the voltage drop across the control resistance 99 and the voltage drop across the direct current winding 95 is approximately equal to the voltage drop between the terminal 101 and the variable tap 112 then the forward current limit rectifier 111 will pass current, which current will flow through the main direct current winding 95 and will oppose the resultant current in this winding 95 which flowing because of the difference in voltage between the tachometer voltage and the speed controlling voltage from the potentiometer 97. By such forward current limit rectifier 111 the total current delivered to the load 87 is limited to a value as established by the setting of the variable tap 112. This is a safety precaution to protect the converter 84 and/ or the load 87. The reverse current limit rectifier 113 will come into play during regeneration, such as when the motor armature 88 is being driven by an overhauling load. During such regeneration the voltage from the tachometer as will generally be in excess of the reference or controlling voltage obtained from the potentiometer 97 by the speed control tap 105 and the flux reversal prevention rectifier 106 will be in use to substantially prevent any resultant voltage being applied to the main direct current winding 95. If the motor armature $8 is being driven by an overhauling load the counterelectromotive force of the motor armature 88 will be greater than the applied electromotive force from the armature of the generator 86, and hence the flow of current will be reversed so that now current rlows from the positive terminal of the motor armature, from right to left through resistor 99, into the positive terminal of the generator armature. This will accordingly reverse the voltage across the control resistance 99 to make suc voltage positive at the right end thereof. If the right end of this control resistance 99 has a greater positive potential thereat than is obtained from the potentiometer 97 by the variable tap 114 relative to the terminal 101 then the reverse current limit rectifier 113 will conduct current through the main direct current Winding 95 which will increase the asymmetric magnetomotive force in the core of the saturable reactor, thus decreasing the reactance of alternating current winding 29, advancing the ignition angle of tube applied to the generator field 85; will develop an increased voltage which is in opposition to the counterelectromotive force of the motor armature 88 to thus limit the regenerative or reverse current caused by the counterelec'tromotive force of the motor armature The control resistance 99 and the resistances between potentiometer taps 1ti1112 and 101-113 should have a low resistance relative to that of the normal speed control circuit comprising the tachometer, the resistor 107 and the resistance between potentiometer taps 101105 in order that the current limit control circuit may readily take command of the control system 83 when an excessive current condition is reached rather than to have the normal speed control circuit remain in command of the control system 83. it is for this reason that resistor 107 is preferably included in the circuit; however, if the remain ing resistance values in the circuit are suitably proportioned, the resistor 107 may be omitted.

Figure 8 shows a modification for part of the circuit diagram shown in Figure 7, wherein a converter 116 supplies energy to a field 117 of a motor 113. The motor armature 119 is supplied from a separate source, not shown. The motor 118 drives a tachometer 89 for deriving a controlled asymmetric electromotive force across positive and negative terminals 103 and 104, respectively. The motor field 117, the mechanical load driven by the motor 118, not shown, and the tachometer 89 may be considered as the load 1.20 of the converter 116. The saturable reactor 93 has been shown as including only the main direct current winding 95 and the alternating current coils 41-42, but it is to be understood that these alternating current coils form part of the passive network 43A, such as is shown in Figure 7. However, in Figure 8, the reactance of the alternating current coils 41-4-2 should preferably be made considerably lower in relation to the reactance of capacity 51 than in Figure 7 so that the initial phase angle of the phase shifter output voltage approximates degrees lagging in the absence of any asy 1;- metric magnetizing energy in the core in order that the output of the converter 116 may never fall below a predetermined minimum value. A passive network A includes the main direct current winding 95 and the potentiometer 97. This potentiometer 97 is or may be the same as the potentiometer 97 of Figure 7, and is arranged for connection to a direct current or asymmetric voltage not shown, which is positive at the left end thereof.

*3 r: reversal prevention rectifier 121 and an optional resistor 122 are serially connected between the positive terminal 193 of the tachometer 89 and the left end of 1114 main direct current winding 95. It will be noted that the crease the output of converter 116. This would conuX reversal prevention rectifier 121 is reversed in polarity tinue until the converter 116 would be delivering its maxicontrol such as is shown in Fig. 7, or with motor armature that the potentiometer tapping 105 had been moved to control, the flux reversal prevention rectifier would be the right for the purpose of obtaining a larger controlling connected with the polarity shown in Figure 7 so that in voltage and therefore a higher speed. The flux reversal the conduction direction of such rectifier the controlled prevention rectifier 123 prevents such undesirable condivoltage or magnetizing energy (tachometer voltage in this tion.

case) is always less than the controlling voltage or mag- 10 Unfortunately, it is difficult to obtain a perfect rectifier, netizing energy. This is because any decrease of speed of and, for instance, a selenium dry plate rectifier requires the motor must increase the difference between these the application of a finite positive voltage of about 0.6 quantities so as to increase saturation of the reactor and volts per plate before it conducts appreciably in the fordeliver more power from the converter to increase the ward direction the presence of such a voltage drop in se speed. With motor field control, such as is shown in the r es with the saturating winding may be undesirable in a rectifier 121 is connected so that in the conducting diquired between a controlling voltage and a controlled rection the controlled voltage or magnetizing energy is voltage derived from the load, particulaily when the latter always greater than the controlling volta e because any is derived from a tachometer and is therefore mall in ecrease of speed must decrease the difference between magnitude. Furthermore, it is believed that the voltage reactor 93 and deliver less power to the motor field so as tion may vary duiing the life of the rectifier, so that when to increase the speed of the motor 118. said rectifier is connected in series with the direct current llie circuit of Figure 9 is a still further modification of saturating windin as in Figures 7 and 8, the calibration the circuit of Figure 7 wherein the power converter 116 of the converter output may vary.

supplies the load 120 as in the circuit of Figure 8, and In cases where a constant calibration of converter outwherein the initial phase angle of the phase shifter output put against controlling voltage is required, the reversalis similar to that of Figure 8 so that the output of the preventing rectifier should preferably be connected in converter 116 can never fall below a predetermined miniparallel with the direct current saturating winding, as in mum value. The load 120 includes the tachometer 89 Figure 9, so as substantially to short-circuit said windelivering a controlled voltage across the terminals 103 ing if the voltage tends to reverse, while having substanand 104 which controlled voltage is combined in opposition tially no effect while the volta e is in the correct sense. to the controlling voltage from the potentiometer 97 0 ensure that the rectifier starts to conduct upon the a between the terminal 101 and the variable tap 105. The plication of even a very small reverse voltage, the rectiresultant of these two voltages, which is the difference fier may be biased to the sharpest point in its voltage-curtherebetween, is applied to the main direct current windrent curve, or to the steepest point or a steep point in ing 95 as in the circuits of Figures 7 and 8. The direct its voltage-resistance curve. For selenium rectifiers the current winding 95 is wound upon the saturable reactor 93 biasing voltage would be about 0.4 volt per plate. Howan it is to be understood that the alternating current ever, even when so biased, the rectifier curve may not be Winding of such saturable reactor is used in a passive netsharp enough to completely prevent reversal of flux. work such as the passive network 43A of the circuit of If we bias the rectifier to +0.4 volt per plate and choose Figure 7 to control the converter 116. The direct current a rectifier of such plate area that its resistance then winding 95 and the potentiometer 97 are part of a passive equals the resistance of the saturating winding, the rectinetwork 9613, which passive network also includes a fiux fier will require a voltage change from +0.2 volt at which reversal prevention rectifier 123, and optionally, a rectifier 45 its resistance is 10 times as great (substantially non-conload resistor 124. The rectifier load resistor 124 interductive) to +0.6 volt at which its resistance is only connects the positive tachometer terminal 103 and the left (substantially a short-circuit across the saturating windend of the main direct current winding 95. The flux reing). In other words, there will be a range of $0.2 volt current winding 95 and a portion of the potentiometer Accordingly, I propose to design it of dry plate rectifiers before such rectifier will pass any mg is below a predetermined value larger voltage than the controlling voltage obtainedfrom value. In the case of a full-wave gas fil variable tap 105 exceedsthe voltage from the tachometer of the saturable reactor.

voltage being appli d to the direct current winding 95 applies a rectified alternating current output to a genera- The converter will thus deliver its predetermined minitor field 129 of the generator 130. e generator armamurn output to the motor field 117 to increase the speed ture 131 supplies a variable direct current voltage to a of the motor 118, and hence the speed of the tachometer load indicated generally at 132 and wh ich comprises a 89 to increase the output voltage thereof and re-establish motor 133 having an armature 134 and a se aratel exa stable condition. If the current through the direct curcited motor field 135. A control system 131? includes a rent winding 95 were permitted to reverse, then the repassive n twork 43A comprising a phase shifter 45 d sultant ma netomotive force in the saturable reactor 93 including the alternating current winding 29 of a saturawould reverse and thereafter increase, and the increasing ble reactor 93 similar to those shown in Figure 7 A maguetomotive fo ce would increase the output of the second passive network 137 includes the main direct curconverter 116 to increase the current to the field 117 rent Winding 95 and an antihunt winding 94 which are thus decreasing the speed of the motor 118. This would wound on the middle leg of the saturable reactor 93 further decrease the volta e output of the tachometer 89 e passive network 137 includes a potentiometer 97 further increasing the difference or resultant voltage beadapted to be energized from some unidirectional or tween the tachometer voltage and the controlling voltage ymm voltage source, h to thus further increase the reversed current applied to the The main direct current winding 95 of th main direct current winding 95, and thus further to inactor 93 is connected be of the load and a terminal 138 on the potentiometer 97. The passive network 137 further includes a feedback or voltage potentiometer 14-9 which has the right end there.- of connected to the negative terminal 141 of the motor armature 134. A series resistor 142 is provided in the motor generator loop circuit between the generator armature 131 and the motor armature 134 and such series resistor is considered as part of the passive network 137. A series potentiometer 143 is connected in shunt with the series resistor 142 in order to obtain finer graduations of voltage steps. The left end of the feedback potentiometer 140 is connected by a variable tap 144 to the series potentiometer 143. An intermediate terminal 145 on the feedback potentiometer 140 is connected by a variable tap 1.46 to the reference potentiometer 97. A reversal prevention rectifier 14-7 is connected between the positive terminal 139 of the load and a tap 148 on the reference potentiometer 97. An antihunt potentiometer 149 is connected in parallel with the field 129 of the generator 130 and a tap 150 obtains an adjustable voltage therefrom which is applied through the antihunt condenser 103 to the antihunt winding 94'.

A feedback voltage in accordance with the voltage delivered to the motor armature 134- is obtained across the feedback potentiometer 140. A certain portion of this voltage, in this case that voltage obtained from the left end of the potentiometer 140 to the left of the intermediate terminal 145, may be considered as a voltage effectively in parallel with at least a part of the load. This feedback voltage is in opposition to a controlling voltage obtained from the left end of the potentiometer 97 between the terminal 138 and the variable tap 146. The reversal prevention rectifier 147 is provided to prevent reversal of the asymmetric magnetomotive force in the core of the saturable reactor 93 and accomplishes this result by effectively short-circuiting the direct current winding 95 should the controlling or reference voltage ever tend to become less than the controlled or feedback voltage from the feedback potentiometer 149. Should this condition occur, the rectifier 147 will conduct current to thus substantially short circuit the main direct current winding 95. The variable tap 148 is provided to establish a small biasing voltage 011' the rectifier 147 to bias this rectifier to the sharpest point on its voltage-current curve or to a steep point in its voltage-resistance curve.

The series potentiometer 143 may be considered as a resistance effectively in series with the load 132 and a voltage may be obtained from this potentiometer 143 by the variable tap 144. Such voltage may be used to obtain a compounding effect such that when the load current increases due to an increasing mechanical load on the motor 133 for example, the voltage drop across this potentiometer 143 will increase, thus to increase the resultant voltage applied to the direct current winding 95 and increase the output of the converter 126. In this arrangement of generator field control the controlled voltage from the feedback potentiometer 140 is arranged to be less than the controlling voltage from the reference potentiometer 97 thus making the right end of the main direct current winding 95 positive relative to the left end thereof. Hence the'resultant or difference of these volt-. ages is applied to the main direct current winding 95.

'The circuit of Figure ll shows a control system 151 as controlling a converter 152 which supplies rectified alternating current power to a load 153. The converter 152 includes a mercury arc rectifier 154 which has two main anodes 156 and 157 supplied from the transformer 155 and, in conjunction with the mercury cathode 158, supplies the rectified power to an armature 159 of a motor 160. The field 16 1 of the motor 160 is supplied from auxiliary anodes 162 and 163, which obtain their power from an additional winding on transformer 155. An ignition electrode 164 is provided in the mercury arc rectifier 154 with the ignition means, not shown. The QQB: trol system 151 includes generally a passive network 167, a saturable reactor 166, and a second passive network 165. The passive network 165 comprises a phase shifter 168 which is similar to the phase shift circuits shown in the copending application Serial No. 770,966, filed August 28, 1947. A secondary winding 169 on the transformer 155 supplies energy to the phase shifter 16%. An inductance 170 has an upper portion 171 thereof serially connected with a resistance 172 across the secondary winding 169 as a reference voltage for the phase shifter 1 A conden r. 1, a d a n u ti e r a tance 1 4 a e as iall sonneetecl a ss he ho f the induc a ce 0- T e' indu t e rea t 1. i h wn a an alt r m tin c rent ind n n the a u a le e cto 66 ha ing a first coil and a second coil 176. A terminal 177 is provided at the juncture of the condenser 173 and the inductive reactance 174 and a grid transformer 179 is connected between such terminal 177 and an end terminal 17$ of the resistance 172, This grid transformer 179 sup: plies an output voltage shiftable in phase to the grids 181 and 182 of the mercury arc rectifier 15.4 from the secondary 183 of such grid transformer. The secondary 183 has a mid tap 184 which connected to the mercury cathode 158 through a source of direct current biasing voltage, which is shown for convenience as a bias bate tery 185. The grid transformer 179 is preferably designed so that its core is sharply saturated by the current in its primary, whereby a sharply peaked output voltage is obtained from its secondary and applied to the grids 181 and 152.

The saturable reactor 166 includes rent coils 175 and 176 on the outer legs thereof and a plurality of direct current windings forming part of the passive network 165 on the middle leg, The passive network 165 differs from the passive networks of Figs. 7, 8, 9 and 10, in that separate direct current windings are provided on the core of the saturable reactor for the purpose of establishing individual asymmetric magnetomotive forces. These direct current windings include a controlling or reference winding 186, a controlled or feedback winding 187, an antihunt winding 188, a current limit winding 189 and a compounding winding 190. A feedback potentiometer 191 is connected between the negative terminal 192 of the motor armature 159 and the cathode 158 of the mercury arc rectifier 154 which is effectively the positive terminal of the converter 152. A series resistor 194 is connected in the loop circuit from the converter 152 to the motor armature 159 between the positive terminal 195 of the armature 159 and a terminal 196 of the load which is connected to the mercury cathode 153. The controlled or feedback winding 187 is connected be? tween the terminal 196 through a biasing potentiometer 197 to an intermediate terminal 193 on the feedback potelntiometer 191. This feedback potentiometer 191 supp ies a the alternating curcontrolled asymmetric electromotive force to the feedback winding 187 which thereby produces a controlled asymmetric magnetomotive force in the core of saturable reactor 166.. Alternately, the feedback winding 187 may be passively connected to the load or converter output, as by direct connection to the terminals 192 and A controlling or reference potentiometer 1198 is provided with a positive terminal 199 and a negative terminal 291} for connection to any suitable asymmetric electromotive force such as a direct current source, not shown, but which may conveniently be derived from the supply to field winding 161. This asymmetric voltage applied to the reference potentiometer 198 may be that derived from the auxiliary anodes 162 and 173 and as such would be in parallel with the field 161, and said reference voltage may be filtered by means, not; shown. The controlling or reference winding 156 is connected between the positive terminal 199 of the reference potentiometer 198 and a variable tap 261, and a filter resistance 202 may be connected in series, and a filter condenser 214 in parallel, as shown. The antihunt winding 18% is connected between the terminal 196 and an intermediate tar 294 on the feedback potentiometer 191 through an antihunt condenser 293. The current limit winding 189 is connected between the positive terminal 195 and a variable tap 205 on the reference potentiometer 198 through a current limit rectifier 296. The compounding winding 1% is connected between the terminal 196 and a variable tap 207 on the series resistor- 194. A reversal prevention rectifier 208 is connected between the variable tap 291 and a tap 299 on the biasing potentiometer 197 through the filter resistor 202 and a filter circuit 210. The filter circuit 219 includes an inductance 211 shunted by a capacitance 217, which are tuned to the predominant ripple frequency, such as 120 cycles, and further includes a'capacitor 215 connected between the terminal 196 and the juncture of the reversal prevention rectifier 298 and the inductance 211. A voltage limiting rectifier 212 is connected between the negative terminal 216 of the reference winding 186 and a tap 213 on' the biasing potentiometer 197. l

In operation, the controllingor reference winding 186 14 has applied thereto from the reference potentiometer 198 ing 186. By connecting the voltage limiting rectifier 212 a controlling asymmetric elcctromotive force which prothrough the variable tap 213 to a point on the biasing duces a controlling asymmetric magnetomotive force in potentiometer 197 which is negative relative to the ter- 6 core of the saturable reactor 166. The controlled or minal 218, the voltage limiting rectifier 212 will normally feedback winding 187 has applied to it a controlled asymnot conduct. Now, when the current limit rectifier 206 metric electromotive force derived from the load, which conducts which ultimately results in decreased volta e pro uces a controlled asymmetric magnetomotive force on the feedback winding 187 as previously described the in the core of the saturable reactor 166 which is in optap 193 on the feedback potentiometer 191 will become position to the controlling magnetomotive force supplied more positive to thereby permit the voltage limiting by the reference winding 186. The anti'l'iunt winding 188, 10 rectifier 212 to pass current, and hence to reduce the as in previously described circuits, applies a magnetomo- Voltage ppl to the reference Wlhdlhg 186 and t0 tive force to the satuiable reactor which stabilizes any 1 ihlt further feduetloh of voltage across the feedback tendency to change a given condition The current limit Wihdlhg 187 Thls W111 reduce the resultant magnetowinding 189 because of its connection through the current motive force In h C r f th satura le reactor 166 to unit rectifier 206, has no voltage theieon until the voltage thus retttlee the Output of the converter 152 It W1 1 across the series resistor 194 exceeds the voltage on t 118 be Seen that the Voltage hmltlhg reetlfief 212 hmlts that part of the reference potentiometer which lies bethe Voltage dltfefehee between the termlhflls 6 and tween the positive terminal 199 and the variable tap 205. 111 Other Words, hmlts t l f r n tW en the Will apply an asymmetric magnetomotive force to the magnetomotive fetee developed y Said pp Wlhdlhgs core of the saturable reactor 166 which is in oppo- 186 and t e y Permit the Current limiting rectisition to the asymmetric magnetomotive force supplied her to function h its P p e by the reference winding 186. The compounding wind- The ym magnetomotive ge produced y the ing 190 has injected therein an asymmetric current which 25 eothPot-thdlhg wlhdthg 190 13 111 addttloh t0 the y flows from the terminal 196 at the left side of series mettle maghetemetlve force 0f the reference in resistor 194 through the winding 190 to the variable hence, as the rneehahleal load f th m t r 160 intap 207. This current produces an asymmetric magr as s (80 as to n as s armat r Curr nt), th netomotive force in the saturable reactor 166 which is etlhteht t0 the eothpotlhdlhg wlhthhg from the Series in addition to the ma n to ti force supplied b h resistor 1 94 will increase thus increasing the resultant reference winding 186 and which is proportional to the e y maghetomotlve force In the Core, n 80 load current so as to increase the resultant asymmetric Increasing the t p Voltage of h Converter 2 Th magnetomot ve fo d thereby to increase h reversal prevention rectifier 208 is e ectively connected put of voltage of th converter 152 as h l d across one end of the reference and feedback windings re t in r a 186 and 187, the other ends of these windings being e vector diagram for the phase shifter 168 will be Connected together- T eh e potentiometer 7 s rather similar to the vector diagram shown in the Figadapted to PF the lhltlal blas 1 1 thlS reversal P ure 3 and the phase shifter operates in substantially the VeIltlOh rectifier 208 So that the Teettfier y become am manner, fully conducting upon the slightest tendency for the The asymmetric magnetomotive force from h f r io voltage difference across these two windings to reverse ence winding 186 is designed to be greater than the h reshltan't esymmetfle'maghetemotlve force- P opposing asymmetric magnetomotive force from the feedtlee; thlS bleslhg Potentlometer 197 earl pp y elthel' 3 ac w d 187 d hence overbaiances h same to positive or a negative bias since the feedback winding apply a resultant asymmetric magnetomotive force to the v 187 15 Preferably e e to have a l r reslstanc saturable reactor 166. Thus, when the speed of the than the reference winding though equal in turns motor 160 drops, less feedback voltage from the feed- Y eheoelhg the feedhaek Winding 187 to he 1 Inner b k potentiometer 191 i applied t th f db k i d. coil having smaller radius and therefore smaller resisting 187, thu increasing th lt t asymmetric ance than the reference winding 186. The filter circuit netomotive force and increasing the output of the con- 210 f the fi e e 1 and r sistor 202 are verter 152 to apply a greater output to the motor arma- 5v PTOVIdeCt t0 InltllmlZe the pp across the r lfi r Z08 ture 159. Since the asymmetric magnetomotive force s that It y he more fi y efieetlver y, the from the current limit winding 189 is in opposition to lhdttetehee 211 and eapacttahee 217 eempflsea reshhaht the asymmetric magnetomotive force from the referelheult resonant t0 the PP frequency Whleh W 1ll be ence winding 186 when the current limit rectifier 206 twice the frequency of e alternahng t pp to is conducting, the asymmetric magnetomotive force from the Converter 152 t s s nant lr uit is used tothe current limit winding will decrease the resultant gethel Wlth thecapacltor 215 to filter the PP across asymmetric magnetomotive force in the core of saturable the feedhaek {Vlndlhg 7- The fi1teI eaPae1t0I in reactor 166 to decrease the output of the converter 152. eonluhetloh W1th the l'eststotj 202 h h hy in some By it bl proportionjng th windings, it may b cases be omitted, filters the ripple which is induced into ranged that the resultant asymmetric magnetomotive the reference Winding from t feedback 'h force is thereafter sharply reduced and that the output 187, and also fitters any PP Whleh y be Present 111 of the converter 152 is thereby sharply limited, the asymmetric electromotive force which is applied to The current limiting rectifier 206 will come into opthe Tefetehee potehtlometer eration When the motor 160 is pulling an excessive load. The elletllt 0f Flgtlfe 12 shows a Control system 220 output of the converter 152 to reduce the speed of the current Power a load 6 08 2221s Sh Wn as a motor 160. is will reduce the voltage applied from motel 223 havlhg it separately eXClted fi d 4 Th conthe feedback potentiometer 191 to the feedback windtrot st 220 Includes generally a PaSSIVe network 225 mg 187 This will reduce the magnetomotive force eomprlslhg a Phase shlfter 226 W ie i s mil r t the produced by this winding which will to some extent, phase shifter used in the Figure 2 The converter 221 innegate the effect of the magnetomotive force from the cludes a transformer 227 Whwh pp s my to th 1y as desired. To improve the functioning of the urshift circuit shown and described in my copending applic" rent limit rectifier 206, the voltage limiting rectifier 212 tiOh Seria1N0-779,909, fi October 1947. The phase h been added to the circuit a a form f h t f shifter 226 includesacondenser 228 and an inductance 229 the feedback winding 187 and the reference Winding whi h are r latively variable to shift the phase of the al- 186. Normally for the motor armature type of control, ternating current voltage, and hence control the output of shown in this Fig. 11, the negative terminal 216 of the the converter 221. In this embodiment the inductance 229 reference winding 186 will be more negative than the is shown as being the alternating current winding of a positive terminal 218 of the biasing potentiometer 197 saturable reactor 230. The saturable reactor is designed in order to make the resultant magnetomotive force in with a permeable core which includes first and second magthe same sense as that produced by the reference windnetic or permeable rails or yokes 231 and 232 with first,

cre d, hird. fourth and fifth legs. 233-231, inclusive, parall l d b tw en these yokes. The first and fifth legs 23}; and237 are, designed to, be saturable by having a small cross sectional area and upon these. legs. are wound the alternating current winding 229 which is the variable inductance of the. phase shifter 226'. Actually, there are two separate coils forming this alternating current winding 229 but it will be understood that one coil or any number of coils may constitute. such winding.

The. second and fourth legs. 234. and 236 preferably have a larger cross sectional area. than the, first and fifth legs. so. that the flux density in these second and fourth legs will not saturate these legs. under normal operating conditions. Thesecond and fourth legs. are designed to accommodate. a plurality of direct current windings. which form. part of the passive netwo k 225. Generally, each of the direct current windings. comprises two coils, one on each of the second and, fourth legs 234. and 23.6.. As. shown in the Figure 12, the second and fourth legs have wound thereon first, sec- 0nd and third direct current windings 238, 239 and 240, respectively; A fourth direct current winding 241 is wound upon the second magnetic yoke 232 between the second and fourth legs, and it likewise is split into. two coils, one on. each side of the third leg 235.

The third leg hasbeen shown as comprising a cylindrical permanent magnet 242. capable of being revolved about its, axis. The permanent magnet 242 is. polarized, not lengthwise of the cylinder, but crosswise, sotthat the north pole lies near a generating line in the surface of the cylinder, and the south pole. lies near a diametrically opposite line in the surface of the cylinder. It will be obvious that the third leg could have short protuberances from the magneticyokes 231 and 232 forming an opening therebetween with the. permanent maget 242 in such opening. The preferred design shown in Figure 12 permits the permanent magnet 242 to be as large as possible, and hence have a maximum of magnetizing energy.

The load 223 has a feedback impedance 243i paralleled thereacross and a series impedance 244 in series there with for obtaining voltages. corresponding to load conditions. The feedback impedance 243 has positive and negative. terminals 245 and 246, respectively, and the series impedance 24-4 likewise has positive and negative terminals 24'7" and 248, respectively. A current limit potentiometer 249 having positive and negative terminals 250- and 251 is adapted to be connected to an external source of direct current or asymmetric. voltage. The positive terminal 251%. is connected to the positive terminal 245 of the feedback potentiometer 243jand hence it will be seen that the potent-iorneters 249. and 243 could be combined into one.

The first direct current winding 238 may be considered as a voltage feedback winding and is connected to. a tap 252 on the feedback potentiometer 243. The positive terminals 245, 247 and 259 are interconnected to establish areference potentia Thus, the tap 252 will be negative relative to the point of reference potential. The other end of the first direct current winding 238 is connected to. the positive terminal 245 or the point of reference potential'. The second direct current winding 239 may be considered as an antihunt winding and is connected between the point of reference potential and a tap 253 on the feedback potentiometer through an antihunt condenser 254. The third direct current winding 240 may be considered as a compounding winding and is connected between the point of reference potential at terminal 247' and a variable tap 255 on the series impedance 244. The fourth direct current winding 241i may be considered as a current limit winding and is connected between the negative terminal 24% of the series impedance 244 and the variable tap 256 on the current limit potentiometer 249 through a current limit rectifier 257 The permanent magnet 242 is. designed to have a mag netizing energy sufficient to exceed the magnetizing energy supplied by the feedback winding 238. The-flux produced by the magnetizing energy from the feedback winding 2-38 is designed to act as a shunt for the flux from the permanent magnet 2-42- and hence divert magnetic lines of force from the first and fifth legs 233 and 23.71 Since the magnetizing energy from the feedback winding 238 is less thanthe magnetizing energy from the permanent magnet 242 it cannot shunt or divert all of the magnetic lines of force, and hence the difference between these two energies will allow a resultant flux to flow in thefirst and-fifth legs:233 and 237, thus resulting in a, given degree of asymmetric j verter tubes; 263

saturation of these legs during normal operating conditions.

Thus, the saturable reactor 23% may be considered to have. a shunt magneticv circuit rather than a series magnetic circuit since a resultant or differential flux is achieved by the shunting of the flux from the permanent magnet 242 rather than by serially opposing its magnetomotive force. The permanent magnet 2.42 may be considered as the controlling magnetizing energy and the energy from the feedback winding 23.3 may be considered as the controlled magnetizing energy. The, fact that the cylindrical permanent magnet 242 is revoluble on its axis permits the amount of controlling magnetizing energy to be varied, and thus the resultant or differential flux applied to the first and fifth legs 233 and 237 can be varied. By such variation the. alternating current impedance of the alternating current winding 229 will vary, and thus control the phase shifter 226. The permanent magnet 242 has been shown in about an ll oclock position, and if it is rotated in the clockwise direction more magnetizing energy will be applied to the entire saturable reactor 230, thus increasing the resultant flux density in the first and fifth legs, 233 and 237, thus decreasing the impedance of the inductance 229 which will shift the phase or the output voltage of the phase shifter 226 ina more leading direction to thus increase the output of the converter 221 which will increase the speed of the motor 223. Conversely, counterclockwise rotation of the ggrsmanent magnet 242 will reduce. the speed of the motor The antihunt winding 239 being connected through the antihunt condenser 254- willv be responsive only to changes of voltage; across the feedback potentiometer 243, and hence will introduce into the saturable reactor 230 a flux component which is dependent only on changes of said voltage for the purpose of stabilizing the operation of the system. The compounding winding 24%), since it obtains a voltage from the series impedance 244, will introduce into. the saturable reactor a flux component which is proportional to the current applied to the load and this fiuX component will be in. opposition to that applied by the feedback winding 23% which will have the effect of increasing, the resultant asyrrn'netric flux in the first and fifth leg-s 233. and 237, thus. increasing the converter output. The current limit winding 2 .1111 normal operation has no voltage impressed thereon since the reactifier 257 prevents current flow until the voltage across the series impedance 244 exceeds the voltage on the current limit potentiometer 24% between the positive terminal 256 and the variable tap 256. When such event occurs, the terminal 248 will be more negative than the variable tap 256, permitting the rectifier 257 to conduct and the current limit winding 241 then impresses a magnetomotive force upon the saturable reactor 23% which opposes the magnetizing energy from the permanent magnet. 2.42, thereby limiting the output of the converter 221 or the speed of the motor 223 to some safe value. The tap 256 is made variable to regulate the point at which this current limiting effect will occur.

A safety feature hasbeen added to the saturable reactor 23.0 which includes generally a polarized control means 258 having two conditions. and being responsive to a tendency toward reversal of the resultant flux in the first leg 233 to change from one to the other of these conditions. The control means 253- in this Figure 12' is shown as a magnetically polarizable armature 259. The armature 259 is pivoted at 254? near its upper end so that the lower end is free, to be attracted to the second magnetic yoke 232. Contacts 261 are actuated by the armature 259 and are shown in the normally closed position with the armature 259' attracted to, the second magnetic yoke 232 which normally is a south pole, thus providing the attraction. The contacts. 26-1 are connected across the condenser 228 so that when the contacts 262 are closed, the output voltage of the phase shifter 226 is equal to the voltage across resistor262- and the voltages applied to the grids of the conand 264 l'agthe voltages applied to their anodes by degrees, thus shutting off any output from the converter 221/ A coil 265 is connected, preferably in series with the motor field 224 so as to polarize the armature 259- with a south pole at its lower, free end, only when said field 224: is energized; Upon such polarization, the armature 259 is. repelled by the magnetic field existing across the leg-233' of the core, which has a south pole at its lower end dueto the permanent magnet 24-2. Thereafter, the converter 221- can supply power to the load and this will result in an opposing magnetization of the leg 23.3"

18 which, however, will not normally alter the'direction'of saidreactor, a plurality of direct current windings on said such magnetization, and accordingly the armature will'norcore, passive means for connecting one of said direct curmally remain repelled and he contacts 261 will remain rent windings to said load to receive an electromotive force open. The control means 2358 provides an additional dependent on a load condition, passive means for consafety feature in the event that the permanent magnet 242 5 neetin another of said direct current windings to said load should be rapidly rotated in a counterclockwise drrection to receive an electromotive force dependent on another when the load 222 has either high mechanical or electrical load ccrrdruon sard windin s cooperatrn with sard eninertia. Under such condition, it would be possible that ergy to establish a resultant asymmetrrc magnetonrotrve the voltage applred to the feedback wrndrng 238 could pro- 'force in sard core, and polarrzed control means to rnhrbrt duce a flux which will not decrease as fast as the rapidly to the effect of reversal of said resultant magnetomotive force ecreasing flux from the permanent magnet 242 and thus in said core. it may be possrble for the resultant flux passing through 2. A control system for a power converter supplying the leg 233 to be reversed Upon such reversal of the reelectric power to a load, comprising a saturable reactor sultant flux Hi the first and fifth legs 233 and 257 an unavrn an alternating current wrndrng forming part of a stable condition would result, for any slight increase in rephase shifting network connectable to said converter for sultant flux would decrease the impedance of the inductcontrol of the output thereof a magnet1zable core in sard ance 229 thus increasing the output of the converter 221 reactor, a plurality of direct current wmdmgs on sard core, to rncrease the vo tage applied to the feedback winding a source of controllrng asymmetric magnetizing energy, a w thus mcreasrn the resultant flux still further The source of controllrng asymmetric electromotive force, a control means 253 prevents any disastrous occurrences 20 source of controlled asymmetric electromotive force deecause should the magnetizing energy produced by the rived directly from the load current, means for connecting feedback winding 238 exceed the magnetizing energy from one of said direct current windings to said load to obtain the permanent magnet 242 for any reason, the left end of a voltage in accordance with a load condition, a nonamthe second magnetic rail 232 would then become polarized plrfymg rectifier, and means for connectrng said controlled with a north pole which would attract the polarized armaand controlling electromotive force sources in series 0pture 259. The armature would then pivot towards the rail position through another of said direct current windings or yoke 232 to close the contacts 261 and thus short the and said rectifier. condenser 228. Upon shorting the condenser 228, the out- 3. control system for a power converter supplying put of the converter 221 will be reduced to a minimum electric power to a load, comprising a saturable reactor l r having an alternating current winding forming part of a in certain applications, for example, where the conphase shifting network connectable to said converter for verter 221 is supplying energy to the field of a motor, it control of the output thereof, said saturable reactor having will then be necessary to reverse the resultant flux in the -a g Core, 8 Source of Controlling asymmetric legs 233 and 237 under conditions of normal operation. magnetizing energy for said reactor and a plurality of This is because with increasing field on a motor the speed direct current windings on said core, one of said windings decreases, and vice versa. Such an arrangement would eing connected to said load to derive a volta e in accordproduce a resultant flux 1n the legs 233 and 237 which is in ance with a load condition, and another of sard direct curthe same direction as the flux which would be produced by rent windings connected to circuit means only responsive the winding 238 alone. In this case the permanent magnet to changes in the output of said converter.

242 may be considered as a shunt for part of the flux pro- 4. In a variable rmpedance network for controlling the e provision of said legs 234 and 236 will circulate through the legs 233 f rhllng part ofsaid variable rmpedance n and 237.

netrzable core in sard reactor, a source of controllrng The operation of this particular circuit arrangement asymmetrrcmagnetizing energy for said reactor, afirst and would b such h h h motor speed decreases, as a second direct current winding on said core, means for with increasing load, the voltage applred to the feedback Connecting Said first direct Current Wlhdlhg efieehvely 111 wrndrng 238 would decrease thus decreasing the resultant P l Wlth at least part of the load to produce a ma flux 1n the legs 233 and 237 to decrease the output of the Iletomotlve force In 0131305111011 to h t u to the Conconverter 221 and hence rncrease the speed of the motor trolling magnetizing energy, means for connectrng said sect will be seen that the polarity of the magnetic yokes 231 0nd direct current winding effectively in series with at least and 232 Will be reversed and hence the polarity of the P of said load to P llee a maghetomotlve force In the polarized ar ature 259 should likewise be reversed in e Sense as the maghetomofive f rC due to the con order that this movable north pole of the armature 259 Will 011mg maghelill'hg y, whereby the Output Voltage of be repelled by the magnetic yoke 232. The leads from the the Conv rter 1s varied to produce a compounding efieet contacts 261 then should be provided to short the alternath h The load Current 1'8 increased, i direct Current ing current winding 229 rather than short the condenser Wlhdlhgs Cooperating with said energy to establish a r 228 so that the converter output will increase to a maxi- 5111mm asymmetric maghethmotl've force in Said Core, and

u upon ever al of the resultant flux in the leg 233, and Polarized control means to inhibit the etfect of reversal of hence apply full field to the motor to reduce its speed to a 6 Sald hm ghetomotive force in aid e ore. mrnrmum n a. varrable rmpedance network for controllrng the In this arrangement, it is preferable that the polarizing P PP to a load by a Converter, the Provision f coil 265 should be connected to a separate source of asyma sathrable reactor having an alternating Current Windlhg metric current and not in series with the motor field. onhlhg P of said Variable impedance network, a ma e claims appended hereto are made a part of the disnetrzable core in said reactor, a source of controllrng closure of this specification and are incorporated herern asymmehle maghetl-Zl'hg energy for Said reactor, 8 PaSSIVe y reference network ncluding a first and a second direct current wind- Although the invention has been described in its premg onsard core, means for connecting said first direct curferred form with a certain degree of particularity, it is rentwmdingto the10ad,means for connectlngsaid second understood that the present disclosure of the preferred dlrect Current winding etTectively in series with at le t orm has been made only by way of example and that part of said load to produce a magnetomotrve force in the numerous changes in the details of circuit construction Same Sense as the maghetomohve f r du to the conand the combrnatron and arrangement of crrcuit elements trolling maghetlzlhg energy, Said direct Current windings may be resorted to without departing from the spirit and cooperating with sard energy to establrsh a resultant asymh scope f th i ti as h i ft laimed, metric magnetomotive force in said core, whereby the outt i l i d i put voltage of the converter is varied in a compounding 1 control system for a power converter including at sense when the load current is increased and a rectrfier least one space discharge device havin a control element connected to sard first direct current winding to rnhrbrt and supplying electrrc power to a load, comprisrng a reversal of sard resultant magnetomotrve force in sard core. phase shift network connected to an alternating current 6. In a variable impedance network for controlling the source and to said control element a reactor. having a power supphed to a load by a converter the provision of a magnetlzable e w th a ome th eof bemg tu able saturable reactor having an alternatrn current winding an avrng an alternatrng current winding on said saturormrng part of sard variable rmpedance network, a ma able core portion forming part of sard phase shrftrnetwork netrzable core in sard reactor, a plurality of direct current magnetizing energy,

' condition, a nonamplifying rectifier, and means for connecting said controlled and controlling electromotive forces in series opposition through another of said direct current windings and said rectifier, thereby to control the output of the converter when the first controlled electromotive force exceeds a predetermined value.

7. In a variable impedance network for controlling a power converter supplying electric power to a load, a saturable reactor having an alternating current winding forming part of said variable impedance network, a magnetizable core in said reactor, a plurality of direct current windings on said core, a source of controlling asymmetric magnetizing energy, a source of controlling asymmetric electromotive force, a source of controlled asymmetric electromotive force derived directly from the load current, and a passive network including, means for connecting one such direct current winding efiectively in parallel with at least part of the load, a polarized control device, and connections between said sources of electromotive forces and said polarized control device and another such direct current winding, whereby said polarized control device permits said first controlled voltage to act in opposition to said controlling voltage to limit the output of the converter when the load current exceeds a predetermined value.

8. In a variable impedance network for controlling a power converter supplying power to a load, the provision of a saturable reactor having an alternating current winding forming part of said variable impedance network, a magnetizable core in said reactor, a plurality of direct current windings on said core, a source of controlling asymmetric magnetizing energy, a source of controlling asymmetric electromotive force, a source of controlled asymmetric electromotive force derived directly from the load current, means for connecting one of said direct current windings to said load to obtain a voltage in accordance with a load condition, a nonamplifying rectifier, means for connecting said controlled and controlling electromotive forces in series opposition through another of said direct current windings and said rectifier, thereby to control the output of the converter controlled electromotive force exceeds a predetermined value, and polarized control means to inhibit the effect of reversal of the magnetmotive force in said core.

9. In a variable impedance network for controlling a power converter supplying electric power to a load, the

provision of a saturable reactor having an alternating current winding forming part of said variable impedance network, a magnetizable core in said reactor, a plurality of direct current windings on said core, a source of controlling asymmetric magnetizing energy, a source of controlling asymmetric electromotive force, a source of controlled asymmetric electromotive force derived directly from the load current, means for connecting one of said direct current windings to said load to obtain a voltage in accordance with a load condition, a nonamplifying rectifier, means for connecting said controlled and controlling electromotive forces in series opposition through another of said direct current windings and said rectifier, thereby to control the output of the converter when the first controlled electromotive force exceeds a predetermined value, and a rectifier connected to said one direct current winding to inhibit reversal of the magnetomotive force in said core.

10. In a variable impedance network for controlling a power converter supplying electric power to a load, the provision of a saturable reactor having an alternating current winding forming part of said variable impedance network, a magnetizable core in said reactor, a plurality of direct current windings on said core, a source of con trolling asymmetric magnetizing energy, a source of controlling asymmetric electromotive force, a source of controlled asymmetric electromotive force derived directly from the load current, means for connecting one of said direct current windings to said load to obtain a voltage in accordance with a load condition, a first nonamplifying rectifier connected to said one direct current winding and to said source of controlling energy to limit the magnetomotive force developed in said core by said one winding in conjunction with said source of controlling energy, a second nonamplifying rectifier, and means for connectwhen the first ing said controlled and controlling electromotive forces said direct current windings and said second rectifier, thereby to control the output of the motive force exceeds a predetermined value.

11. In a variable impedance network for controlling a power converter supplying electric power to a load, a saturable reactor having an alternating current winding forming part of said variable impedance network, said saturable reactor having a magnetizable core, a source of controlling asymmetric magnetizing energy for said reactor, and a plurality of direct current windings on said core, one of said windings being connected to said load to derive a voltage in accordance with a load condition, and another of said direct current windings connected to circuit means responsive only to changes in the output of said converter.

12. In a variable impedance network for controlling a power converter supplying electric power to a load, a saturable reactor having an alternating current winding forming part of said variable impedance network, said saturable reactor having a magnetizable core, a source of controlling asymmetric magnetizing energy for said reactor, a plurality of direct current windings on said core, one of said windings being connected to said load to derive a voltage in accordance with a load condition, and another of said direct current windings connected to circuit means only responsive to changes in the output of said converter, and polarized control means to inhibit the effect of reversal of the asymmetric magnetomotive force in said core.

13. In a variable impedance network for controlling a power converter supplying electric power to a load, a saturable reactor having an alternating current winding forming part of said variable impedance network, said saturable reactor having a magnetizable core, a source of controlling asymmetric magnetizing energy for said reactor, a plurality of direct current windings on said core, one of said windings being connected to said load to derive a voltage in accordance with a load condition, and another of said direct current windings connected to circuit means only responsive to changes in the output of said converter, and a rectifier connected to said one direct current winding to inhibit reversal of the asymmetric magnetomotive force in said core.

14. An electrical control system for a power converter for supplying electric power to a load, comprising a phase shifting network operable from an alternating current source and controlling said converter, said phase shifting network including a capacitive reactance serially connected to a variable inductive reactance having one output terminal connected therebetween, means for energizing said reactances from a reference voltage derived from said A. source such that the potential of said output terminal lies, in a voltage vector diagram, on an arc spanning the reference voltage vector, circuit elements energrzed from said A. C. source, a second output terminal associated with said circuit elements such that the potentlal of said second output terminal lies, in the vector diagram, within the space bounded by said reference voltage vector and said arc, a core in said inductive winding, first and second direct current windings on said core, said control system also including a source of controlling asymmetric voltage, means for connecting said first windmg to said controlling source to establish an asymmetric magnetomotive force in said core, means for supplying directly to said second winding from said load a voltage representative of an operating condition of the load to produce an opposing asymmetric magnetomotive force, the difference between said magnetmotive forces producmg a resultant asymmetric magnetomotive force in said core.

15. The combination of claim 14, including polarized control means to inhibit the effect of reversal of the asymmetric magnetomotive force.

16. The combination of claim 15 wherein said polarized control means prevents reversal in direction of the resultant magnetomotive force.

17. The combination of claim 15, including a rectifier connected between said two windings so as to become conducting if the magnetomotive force which is normally the larger tends to become the smaller, whereby such magnetomotive force can never become the smaller one and accordingly the direction of the resultant magnetomotive force is prevented from reversing.

19. The combination of claim is in the same sense as the magnetomotive force produced y said first controlling voltage to act as a means for compounding References Cited in the file of this patent Number UNITED STATES PATENTS Name Date West Apr. 30, 1929 Alexanderson July 4, 1933 Fitz Gerald Sept. 12, 1933 Schmidt Apr. 10, 1934 Logan Apr. 27, 1937 Demontvignier Feb. 13, 1940 Claesson Dec. 29, 1942 Bendz Apr. 18, 1950 King June 26, 1951 Hedstrom May 13, 

